Amniotic fluid embolism to lung
Amniotic fluid embolism is a special type of pulmonary embolism where the embolus is comprised of amniotic fluid. It can be a highly fatal complication of pregnancy, with an 80% maternal mortality rate.
It is thought to complicate 1/8000-80,000 pregnancies.
The classic clinical presentation is of abrupt dyspnoea, cyanosis, and shock, shortly followed by a cardiorespiratory arrest and severe pulmonary oedema. Some patients may present with an anaphylactic reaction caused by a hypersensitivity to the leukotrienes and arachnoid metabolites present in amniotic fluid. Central nervous system irritability producing convulsions is also considered a typical feature.
It occurs when amniotic fluid is forced into the bloodstream through small tears in uterine veins during normal labour. However, in some cases, the placenta is disrupted by surgery or trauma.
- approximately 40% of patients may suffer a consumptive coagulopathy 2
Non-specific but may have diffuse bilateral heterogeneous and homogeneous areas of increased opacity (can be indistinguishable from acute pulmonary oedema due to other causes).
Chest CT may show diffuse ground glass opacities (similar to early stage of acute respiratory distress syndrome) and prominent hilar pulmonary vasculature 9. CT findings are also not specific and difficult to distinguish from other causes of acute noncardiogenic or cardiogenic pulmonary oedema.
History and etymology
It was first reported by Ricardo Meyer in 1926 6.
- 1. Han D, Lee KS, Franquet T et-al. Thrombotic and nonthrombotic pulmonary arterial embolism: spectrum of imaging findings. Radiographics. 2003;23 (6): 1521-39. Radiographics (full text) - doi:10.1148/rg.1103035043 - Pubmed citation
- 2. Rossi SE, Goodman PC, Franquet T. Nonthrombotic pulmonary emboli. AJR Am J Roentgenol. 2000;174 (6): 1499-508. doi:10.2214/ajr.174.6.1741499 - Pubmed citation
- 3. Pahade JK, Litmanovich D, Pedrosa I et-al. Quality initiatives: imaging pregnant patients with suspected pulmonary embolism: what the radiologist needs to know. Radiographics. 2009;29 (3): 639-54. Radiographics (full text) - doi:10.1148/rg.293085226 - Pubmed citation
- 4. Rudra A, Chatterjee S, Sengupta S et-al. Amniotic fluid embolism. Indian J Crit Care Med. 2009;13 (3): 129-35. doi:10.4103/0972-5229.58537 - Free text at pubmed - Pubmed citation
- 5. Knight M, Tuffnell D, Brocklehurst P et-al. Incidence and risk factors for amniotic-fluid embolism. Obstet Gynecol. 2010;115 (5): 910-7. doi:10.1097/AOG.0b013e3181d9f629 - Pubmed citation
- 6. Meyer JR. Embolia pulmonar amnio-caseosa. Braz Med. 1926;2:301–3
- 7. Kramer MS, Rouleau J, Baskett TF et-al. Amniotic-fluid embolism and medical induction of labour: a retrospective, population-based cohort study. Lancet. 2006;368 (9545): 1444-8. doi:10.1016/S0140-6736(06)69607-4 - Pubmed citation
- 8. Gilbert WM, Danielsen B. Amniotic fluid embolism: decreased mortality in a population-based study. Obstet Gynecol. 1999;93 (6): 973-7. Pubmed citation
- 9. Imanaka H, Takahara B, Yamaguchi H et-al. Chest computed tomography of a patient revealing severe hypoxia due to amniotic fluid embolism: a case report. J Med Case Rep. 2010;4 (1): 55. doi:10.1186/1752-1947-4-55 - Free text at pubmed - Pubmed citation